CN108855095B - Preparation method of multi-core shell hollow catalyst nickel-nickel silicate-SiO2 for methane reforming - Google Patents

Abstract

The invention discloses a method for preparing a multi-core shell hollow catalyst nickel-nickel silicate-SiO ₂ for methane reforming, which is characterized in that the method comprises the following steps: (1) firstly preparing silica nanoparticles; (2) Take silica nanoparticles with a particle size of 500nm to 1µm and prepare them to a concentration of 1g/L to 10g/L, add alkaline solution to adjust the pH to 8-13, and add a nickel precursor with a concentration of 1g/L to 10g/L, Synthesize nickel silicate hollow spheres at a temperature of 50 ^o C to 220 ^o C; (3) disperse the nickel silicate hollow spheres in a mixed solution of surfactant and water, add lye after stirring, The pH was adjusted to 10-14, and 10 mL of ethyl orthosilicate was added to react at room temperature to obtain nickel silicate-SiO ₂ core-shell hollow spheres; (4) The nickel silicate-SiO ₂ core-shell hollow spheres were placed in Reduction in a hydrogen atmosphere at a temperature of 300 ^o C to 800 ^o C yields a highly dispersed nickel-nickel silicate-SiO ₂ multi-core shell hollow catalyst. The catalyst prepared by the invention has the advantages of high anti-sintering, anti-carbon deposition, high temperature stability and high specific surface area.

Description

Preparation method of multi-core shell hollow catalyst nickel-nickel silicate-SiO2 for methane reforming

technical field

The invention relates to a preparation method of a multi-core shell hollow catalyst nickel-nickel silicate-SiO ₂ for methane reforming, and belongs to the technical field of chemical production.

Background technique

Nickel-based catalysts have been widely studied at home and abroad because of their low price and high reforming catalytic activity. When they are applied to _CH4 dry reforming reaction, the carbon deposition phenomenon of nickel-based catalysts is relatively serious, mainly due to the sintering of nickel metal. Promote the occurrence of carbon deposition side reactions. Especially when the CH ₄ dry reforming reaction temperature is lower than 600 ^o C, the carbon deposition phenomenon is more serious. The inventors of the present invention have developed a core-shell structure catalyst, which can effectively prevent metal sintering. However, these core-shell structures generally suffer from low specific surface area and low mass transfer efficiency.

Metal silicates are widely used as catalysts due to their low price, high temperature stability, and high specific surface area. However, these metal silicates are currently only used as catalyst precursors. After high temperature reduction, the metal silicates are completely decomposed and lose their advantages of high specific surface area.

That is, there is a need for a multi-core-shell hollow catalyst for methane reforming, which still has high carbon deposition resistance, high specific surface area and anti-sintering properties under the condition of CH ₄ dry reforming reaction temperature of 600 ^o C.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a method for preparing a multi-core shell hollow catalyst for methane reforming, nickel-nickel silicate-SiO ₂ , which still has high sintering resistance under the condition that the CH ₄ dry reforming reaction temperature is 600 ^o C. , anti-carbon deposition, high temperature stability and high specific surface area to overcome the shortcomings of the existing technology.

The technical scheme of the present invention is: a preparation method of a multi-core shell hollow catalyst nickel-nickel silicate-SiO ₂ for methane reforming, the method comprises the following steps: (1) ethanol, water and silicon source are heated at 0 ^o C ~ Mix and stir evenly under the condition of 70 ^o C, then add alkaline solution to adjust the pH to 10, stir, separate by centrifuge, wash, and finally dry to obtain silica nanoparticles; Silicon nanoparticles are prepared to a concentration of 1g/L～10g/L, add alkaline solution to adjust the pH to 8-13, add a nickel precursor with a concentration of 1g/L～10g/L, at a temperature of 50 ^o C～220 ^o C Synthesize under the conditions, and finally obtain nickel silicate hollow spheres through cooling, centrifugation and washing; (3) disperse the nickel silicate hollow spheres in a mixed solution of surfactant and water, add lye after stirring, Adjust the pH to 10-14, add 10 mL of ethyl orthosilicate to react at room temperature, and finally centrifuge, wash, and dry to obtain nickel silicate-SiO ₂ core-shell hollow spheres; (4) The nickel silicate -SiO2 core _- shell hollow spheres were reduced in a hydrogen atmosphere at a temperature of 300 ^oC to 800 ^oC to obtain a highly dispersed nickel-nickel silicate- _SiO2 multicore-shell hollow catalyst.

In the above step (1), the silicon source is one or a combination of ethyl orthosilicate, sodium silicate water glass, and methyl orthosilicate.

In the above step (2), the nickel precursor is one or a combination of nickel nitrate, nickel acetate, nickel acetylacetonate, nickel oxalate, and nickel oleate.

In the above steps (1), (2), (3), the alkaline solution is one or a combination of sodium hydroxide, urea, and ammonia water.

In the above steps (1), (2) and (3), the washing solvent used for washing is one or a combination of water, ethanol, methanol, acetone and cyclohexane.

In the above-mentioned step (3), the surfactant is a nonionic surfactant or an ionic surfactant, wherein the nonionic surfactant is C ₁₄ H ₂₂ O(C ₂ H ₄ O) _n , n=10～15, one or more of C ₁₅ H ₂₄ O(C ₂ H ₄ O) _n , n=5～10; ionic surfactant is alkyl quaternary ammonium salt surfactant C _n TAB, one or more of n=10～15.

In the aforementioned step (4), the specific surface area of the nickel-nickel silicate-silica core-shell hollow catalyst is 300m ² •g ^-1 to 600m ² •g ^-1 , and the thickness of the silica shell is 30nm to 80nm.

Compared with the prior art, the preparation method of the multi-core-shell hollow catalyst nickel-nickel silicate-SiO ₂ for methane reforming of the present invention comprises the following steps: (1) ethanol, water and silicon source at 0 ^o C ~ Mix and stir evenly under the condition of 70 ^o C, then add alkaline solution to adjust the pH to 10, stir, separate by centrifuge, wash, and finally dry to obtain silica nanoparticles; Silicon nanoparticles are prepared to a concentration of 1g/L～10g/L, add alkaline solution to adjust the pH to 8-13, add a nickel precursor with a concentration of 1g/L～10g/L, at a temperature of 50 ^o C～220 ^o C Synthesize under the conditions, and finally obtain nickel silicate hollow spheres through cooling, centrifugation and washing; (3) disperse the nickel silicate hollow spheres in a mixed solution of surfactant and water, add lye after stirring, Adjust the pH to 10-14, add 10 mL of ethyl orthosilicate to react at room temperature, and finally centrifuge, wash, and dry to obtain nickel silicate-SiO ₂ core-shell hollow spheres; (4) The nickel silicate -SiO2 core _- shell hollow spheres were reduced in a hydrogen atmosphere at a temperature of 300 ^oC to 800 ^oC to obtain a highly dispersed nickel-nickel silicate- _SiO2 multicore-shell hollow catalyst. The nickel-nickel silicate- _SiO2 prepared by such a method has high dispersity (particle size between 2nm and 7nm) and high resistance to carbon deposition (carbon deposition <11%), especially in _CH4 dry reforming Under the condition of reaction temperature of 600 ^o C, it still has high anti-coking performance. Compared with the existing catalysts with high anti-coking performance only above 700 ^o C, it has obvious advantages and wider applicability; at the same time, It has high specific surface area (300m ² ·g ^-1 ～600m ² ·g ^-1 ), strong metal-support interaction (reduction temperature above 655 ^o C), and high mass transfer efficiency. The nickel nanoparticles are dispersed in the nickel silicate hollow spheres and the SiO ₂ shell to form a multi-core shell hollow structure with a particle size of 500nm-1µm. Compared with the existing CH ₄ dry reforming nickel-based catalysts, the synthesis method is fast, Synthetic raw materials are readily available, large-scale synthesis can be achieved, and the synthesized catalyst has high specific surface area, high dispersion, strong metal-support interaction, high mass transfer efficiency, and good anti-carbon performance.

Description of drawings

Figure 1 is a schematic diagram of the preparation method of the nickel-nickel silicate-SiO ₂ polycore shell hollow type.

Figure 2 is a transmission electron microscope image of nickel silicate hollow spheres.

Figure 3 is a high-resolution transmission electron microscope image of nickel silicate hollow spheres.

Figure 4 is a transmission electron microscope image of nickel silicate-SiO ₂ core-shell hollow spheres.

Figure 5 is a high-resolution transmission electron microscope image of nickel silicate-SiO ₂ core-shell hollow spheres.

Figure 6 is a transmission electron microscope image of a nickel-nickel silicate-SiO ₂ multicore shell hollow type catalyst.

Figure 7 is a high-resolution transmission electron microscope image of the nickel-nickel silicate-SiO ₂ multicore-shell hollow catalyst.

Figure 8 is a temperature-programmed reduction graph of Ni-silicate hollow spheres-Ni-Si core _- shell hollow spheres.

Fig. 9 is a graph showing the reaction activity of CH ₄ dry reforming of nickel silicate hollow sphere-nickel silicate-SiO ₂ core-shell hollow catalyst.

Figure 10 is a thermogravimetric analysis diagram of nickel silicate hollow spheres-nickel silicate-SiO core _- shell hollow catalyst after CH ₄ dry reforming reaction.

Detailed ways

Preparation method of multi-core shell hollow catalyst nickel-nickel silicate-SiO ₂ for methane reforming, ethanol, water and silicon source are mixed and stirred evenly under the condition of 0 ^o C ~ 70 ^o C, and then lye is added to adjust pH to 10 , stirring, centrifuging, washing, and finally drying to obtain silica nanoparticles; take silica nanoparticles with a particle size of 500nm to 1µm to prepare a concentration of 1g/L to 10g/L, and add lye to adjust the pH to 8-13, add nickel precursor with a concentration of 1g/L to 10g/L, synthesize at a temperature of 50 ^o C to 220 ^o C, and finally obtain nickel silicate hollow spheres through cooling, centrifugation and washing ; Disperse the nickel silicate hollow spheres in the mixed solution of surfactant and water, add lye after stirring, adjust the pH to 10-14, add 10 mL of ethyl orthosilicate to react at room temperature, and finally centrifuge , washing and drying to obtain nickel silicate-SiO ₂ core-shell hollow spheres; reducing nickel silicate-SiO ₂ core-shell hollow spheres in a hydrogen atmosphere at a temperature of 300 ^o C to 800 ^o C to obtain highly dispersed Nickel-nickel silicate- _SiO2 multicore shell hollow catalyst.

Example 1:

(1) Mix 200 mL of ethanol, 100 mL of water and 40 mL of methyl orthosilicate at 0 ^o C and stir well. Urea was added to adjust the pH to 10. After stirring for 2 h, it was separated with a centrifuge. Wash with a mixture of methanol and water. Finally, 600nm silica nanoparticles were obtained, which were dried at 150 ^° C for 24h.

(2) Take 2g silicon dioxide, 0.3g nickel nitrate, add ammonia water, adjust pH to 8. The mixed solution was put into an autoclave, heated to 50 degrees, reacted for 24 hours, and then cooled to room temperature. Centrifuged, washed with methanol, ethanol, and water, and put it into a drying oven at 100 degrees. The nickel silicate hollow spheres were obtained (as shown in Figures 2 and 3), with a specific area of 250m ² ·g ^-1 .

(3) Disperse the nickel silicate hollow spheres in a mixed solution of ethanol (30 mL), water (10 mL), and C _n TAB (n=10) (30 mg). After stirring for 30 min, ammonia water (30 mL) was added. The pH was adjusted to 10, and after stirring for 30 min, 10 mL of ethyl orthosilicate was added. After reacting at room temperature for 48 h, the mixture was centrifuged and washed three times with a mixed solution of methanol and water. Put it in a drying oven at 100 ^o C to dry for 24h. Nickel silicate-SiO ₂ core-shell hollow spheres are obtained, the thickness of the SiO ₂ shell is 40 nm, and the specific surface area is 400 m ² ·g ^-1 (as shown in Figures 4 and 5).

(4) The nickel silicate-SiO ₂ core-shell hollow spheres were placed in a muffle furnace and calcined at 700 degrees for 4 h. Then pure hydrogen was introduced and reduced at 700 degrees for 0.5h. Finally, a nickel-nickel silicate-SiO ₂ multi-core shell hollow sphere catalyst was obtained (as shown in Fig. 6, 7). It can be seen from Figures 6 and 7 that despite the high temperature calcination and reduction, the needle-like nickel silicate phase still exists. It can be seen that in the catalyst obtained by this synthesis method, the nickel silicate is not completely decomposed. The particle size of the highly dispersed nickel is about 5 nm. In addition, compared with the nickel silicate hollow sphere catalyst, the nickel silicate-SiO core _- shell hollow sphere catalyst has a higher reduction temperature, indicating that the core-shell catalyst has a higher strong metal-support interaction (Fig. 8). shown).

(5) Under normal pressure, pass CH ₄ , CO ₂ and He into nickel-nickel silicate hollow spheres in a 1:1:1 manner (space velocity 36L·g ^-1 cat·h ^-1 ), respectively And nickel-nickel silicate-SiO ₂ multi-core shell hollow catalyst fixed bed reactor (600 ^o C), reaction 50h. For the nickel-nickel silicate hollow sphere catalyst, although the initial conversion is slightly higher because of its higher nickel loading. However, the conversion of methane and carbon dioxide dropped by 36% and 31%, respectively. In contrast, for the nickel-nickel silicate-SiO core _- shell hollow sphere catalyst, the conversions of methane and carbon dioxide dropped by 23% and 20%, respectively (Fig. 9). Thermogravimetric differential thermal analysis shows that the nickel-nickel silicate-SiO ₂ multi-core-shell hollow sphere catalyst has only 1/7 the weight loss of the nickel-nickel silicate-SiO ₂ core-shell hollow sphere catalyst. , indicating that the former has high resistance to carbon deposition (Fig. 10).

Example 2:

(1) Mix 200 mL of ethanol, 100 mL of water and 40 mL of methyl orthosilicate at 35 ^o C and stir well. Urea was added to adjust the pH to 10. After stirring for 2 h, it was separated with a centrifuge. Wash with a mixture of methanol and water. Finally, 600nm silica nanoparticles were obtained, which were dried at 150 ^° C for 24h.

(2) Take 2g of silicon dioxide and 0.3g of nickel nitrate, add ammonia water, and adjust the pH to 11. The mixed solution was put into an autoclave, heated to 50 degrees, reacted for 24 hours, and then cooled to room temperature. Centrifuged, washed with methanol, ethanol, and water, and put it into a drying oven at 100 degrees. The nickel silicate hollow spheres were obtained (as shown in Figures 2 and 3), with a specific area of 250m ² ·g ^-1 .

(3) Disperse the nickel silicate hollow spheres in a mixed solution of ethanol (30 mL), water (10 mL), and C _n TAB (n=10) (30 mg). After stirring for 30 min, ammonia water (30 mL) was added. The pH was adjusted to 12, and after stirring for 30 min, 10 mL of ethyl orthosilicate was added. After reacting at room temperature for 48 h, the mixture was centrifuged and washed three times with a mixed solution of methanol and water. Put it in a drying oven at 100 ^o C to dry for 24h. Nickel silicate-SiO ₂ core-shell hollow spheres are obtained, the thickness of the SiO ₂ shell is 40 nm, and the specific surface area is 400 m ² ·g ^-1 (as shown in Figures 4 and 5).

(4) The nickel silicate-SiO ₂ core-shell hollow spheres were placed in a muffle furnace and calcined at 700 degrees for 4 h. Then pure hydrogen was introduced and reduced at 700 degrees for 0.5h. Finally, a nickel-nickel silicate-SiO ₂ multi-core shell hollow sphere catalyst was obtained (as shown in Fig. 6, 7). It can be seen from Figures 6 and 7 that despite the high temperature calcination and reduction, the needle-like nickel silicate phase still exists. It can be seen that in the catalyst obtained by this synthesis method, the nickel silicate is not completely decomposed. The particle size of the highly dispersed nickel is about 5 nm. In addition, compared with the nickel silicate hollow sphere catalyst, the nickel silicate-SiO core _- shell hollow sphere catalyst has a higher reduction temperature, indicating that the core-shell catalyst has a higher strong metal-support interaction (Fig. 8). shown).

(5) Under normal pressure, pass CH ₄ , CO ₂ and He into nickel-nickel silicate hollow spheres in a 1:1:1 manner (space velocity 36L·g ^-1 cat·h ^-1 ), respectively And nickel-nickel silicate-SiO ₂ multi-core shell hollow sphere catalyst fixed bed reactor (600 ^o C), the reaction 50h. For the nickel-nickel silicate hollow sphere catalyst, although the initial conversion is slightly higher because of its higher nickel loading. However, the conversion of methane and carbon dioxide dropped by 36% and 31%, respectively. In contrast, for the nickel-nickel silicate-SiO core _- shell hollow sphere catalyst, the conversions of methane and carbon dioxide drop by 19% and 22%, respectively. Thermogravimetric differential thermal analysis shows that the nickel-nickel silicate-SiO ₂ multi-core shell hollow sphere catalyst has a weight loss of 1/8 of that of the nickel-nickel silicate catalyst, indicating that the former has high resistance to carbon deposition.

Example 3:

(1) Mix 200 mL of ethanol, 100 mL of water and 40 mL of methyl orthosilicate at 70 ^o C and stir well. Urea was added to adjust the pH to 10. After stirring for 2 h, it was separated with a centrifuge. Wash with a mixture of methanol and water. Finally, 600nm silica nanoparticles were obtained, which were dried at 150 ^° C for 24h.

(2) Take 2g of silica and 0.3g of nickel nitrate, add ammonia water, and adjust the pH to 13. The mixed solution was put into an autoclave, heated to 50 degrees, reacted for 24 hours, and then cooled to room temperature. Centrifuged, washed with methanol, ethanol, and water, and put it into a drying oven at 100 degrees. The nickel silicate hollow spheres were obtained (as shown in Figures 2 and 3), with a specific area of 250m ² ·g ^-1 .

(3) Disperse the nickel silicate hollow spheres in a mixed solution of ethanol (30 mL), water (10 mL), and C _n TAB (n=10) (30 mg). After stirring for 30 min, ammonia water (30 mL) was added. The pH was adjusted to 14, and after stirring for 30 min, 10 mL of ethyl orthosilicate was added. After reacting at room temperature for 48 h, the mixture was centrifuged and washed three times with a mixed solution of methanol and water. Put it in a drying oven at 100 ^o C to dry for 24h. Nickel silicate-SiO ₂ core-shell hollow spheres are obtained, the thickness of the SiO ₂ shell is 40 nm, and the specific surface area is 400 m ² ·g ^-1 (as shown in Figures 4 and 5).

(4) The nickel silicate-SiO ₂ core-shell hollow spheres were placed in a muffle furnace and calcined at 700 degrees for 4 h. Then pure hydrogen was introduced and reduced at 700 degrees for 0.5h. Finally, a nickel-nickel silicate-SiO ₂ multi-core shell hollow sphere catalyst was obtained (as shown in Fig. 6, 7). It can be seen from Figures 6 and 7 that despite the high temperature calcination and reduction, the needle-like nickel silicate phase still exists. It can be seen that in the catalyst obtained by this synthesis method, the nickel silicate is not completely decomposed. The particle size of the highly dispersed nickel is about 5 nm. In addition, compared with the nickel silicate hollow sphere catalyst, the nickel silicate-SiO core _- shell hollow sphere catalyst has a higher reduction temperature, indicating that the core-shell catalyst has a higher strong metal-support interaction (Fig. 8). shown).

(5) Under normal pressure, pass CH ₄ , CO ₂ and He into nickel-nickel silicate hollow spheres in a 1:1:1 manner (space velocity 36L·g ^-1 cat·h ^-1 ), respectively And nickel-nickel silicate-SiO ₂ multi-core shell hollow sphere catalyst fixed bed reactor (600 ^o C), the reaction 50h. For the nickel-nickel silicate hollow sphere catalyst, although the initial conversion is slightly higher because of its higher nickel loading. However, the conversion of methane and carbon dioxide dropped by 36% and 31%, respectively. In comparison, for the nickel-nickel silicate-SiO core _- shell hollow sphere catalyst, the conversions of methane and carbon dioxide drop by 30% and 29%, respectively. Thermogravimetric differential thermal analysis shows that the nickel-nickel silicate-SiO ₂ multi-core shell hollow sphere catalyst has a weight loss of 90% of that of the nickel-nickel silicate catalyst, indicating that the former has high resistance to carbon deposition.

Example 4:

(1) 200 mL of ethanol, 100 mL of water and 40 mL of methyl orthosilicate were mixed and stirred evenly at room temperature. Urea was added to adjust the pH to 10. After stirring for 2 h, it was separated with a centrifuge. Wash with a mixture of methanol and water. Finally, 600nm silica nanoparticles were obtained, which were dried at 150 ^° C for 24h.

(2) Take 2g of silica and 0.3g of nickel nitrate, add ammonia water, and adjust the pH to 12. The mixed solution was put into an autoclave, heated to 120 degrees, reacted for 24 hours, and then cooled to room temperature. Centrifuged, washed with methanol, ethanol, and water, and put it into a drying oven at 100 degrees. The nickel silicate hollow spheres were obtained (as shown in Figures 2 and 3), with a specific area of 250m ² ·g ^-1 .

(3) Disperse the nickel silicate hollow spheres in a mixed solution of ethanol (30 mL), water (10 mL), and C _n TAB (n=10) (30 mg). After stirring for 30 min, ammonia water (30 mL) was added. After stirring for 30 min, 10 mL of ethyl orthosilicate was added. After reacting at room temperature for 48 h, the mixture was centrifuged and washed three times with a mixed solution of methanol and water. Put it in a drying oven at 100 ^o C to dry for 24h. Nickel silicate-SiO ₂ core-shell hollow spheres are obtained, the thickness of the SiO ₂ shell is 40 nm, and the specific surface area is 400 m ² ·g ^-1 (as shown in Figures 4 and 5).

(4) The nickel silicate-SiO ₂ core-shell hollow spheres were placed in a muffle furnace and calcined at 700 degrees for 4 h. Then pure hydrogen was introduced and reduced at 700 degrees for 0.5h. Finally, a nickel-nickel silicate-SiO ₂ multi-core shell hollow sphere catalyst was obtained (as shown in Fig. 6, 7). It can be seen from Figures 6 and 7 that despite the high temperature calcination and reduction, the needle-like nickel silicate phase still exists. It can be seen that in the catalyst obtained by this synthesis method, the nickel silicate is not completely decomposed. The particle size of the highly dispersed nickel is about 5 nm. In addition, compared with the nickel silicate hollow sphere catalyst, the nickel silicate-SiO core _- shell hollow sphere catalyst has a higher reduction temperature, indicating that the core-shell catalyst has a higher strong metal-support interaction (Fig. 8). shown).

(5) Under normal pressure, pass CH ₄ , CO ₂ and He into nickel-nickel silicate hollow spheres in a 1:1:1 manner (space velocity 36L·g ^-1 cat·h ^-1 ), respectively And nickel-nickel silicate-SiO ₂ multi-core shell hollow sphere catalyst fixed bed reactor (600 ^o C), the reaction 50h. For the nickel-nickel silicate hollow sphere catalyst, although the initial conversion is slightly higher because of its higher nickel loading. However, the conversion of methane and carbon dioxide dropped by 36% and 31%, respectively. In contrast, for the nickel-nickel silicate-SiO core _- shell hollow sphere catalyst, the conversions of methane and carbon dioxide dropped by 23% and 20%, respectively (Fig. 9). Thermogravimetric differential thermal analysis shows that the weight loss of the nickel-nickel silicate-SiO ₂ multi-core shell hollow sphere catalyst is only 1/7 of that of the nickel-nickel silicate catalyst, indicating that the former has high resistance to carbon deposition (Fig. 10). .

Example 5:

(1) Mix 200 mL of ethanol, 100 mL of water and 10 mL of sodium silicate at 0 ^o C and stir well. Ammonia was added to adjust the pH to 10. After stirring for 2 h, it was separated with a centrifuge. Wash with a mixture of ethanol and water. Finally, silica nanoparticles of 200 nm were obtained, which were dried at 150 degrees for 24 hours.

(2) Take 2g silicon dioxide, 0.3g nickel acetate, add sodium hydroxide, adjust pH to 12. The mixed solution was put into an autoclave, heated to 120 degrees, reacted for 24 hours, and then cooled to room temperature. After centrifugation and washing with methanol, ethanol, and water, prevent from drying oven at 100 ^o C. Nickel silicate hollow spheres were obtained. The specific area was 230 m ² ·g ^-1 .

(3) Disperse the nickel silicate hollow spheres in a mixed solution of ethanol (30 mL), water (10 mL), and C _n TAB (n=10) (30 mg). After stirring for 30 min, ammonia water (30 mL) was added. After stirring for 30 min, 30 mL of ethyl orthosilicate was added. After reacting at room temperature for 80 h, the mixture was centrifuged and washed three times with a mixed solution of methanol and water. Put it in a drying oven at 100 ^o C to dry for 24h. The nickel silicate-SiO ₂ core-shell hollow spheres were obtained, the thickness of the SiO ₂ shell layer was 80 nm, and the specific surface area was 600 m ² ·g ^-1 .

(4) The nickel silicate-SiO ₂ core-shell hollow spheres were placed in a muffle furnace and calcined at 700 degrees for 4 h. Then pass 5% hydrogen, and reduce at 700 degrees for 0.5h. Finally, a nickel-nickel silicate-SiO ₂ multi-core shell hollow sphere catalyst was obtained. Despite high temperature calcination and reduction, the needle-like nickel silicate phase still exists. It can be seen that in the catalyst obtained by this synthesis method, the nickel silicate is not completely decomposed. The particle size of the highly dispersed nickel is about 6 nm. In addition, compared with the nickel silicate hollow sphere catalyst, the nickel silicate-SiO core _- shell hollow sphere catalyst has a higher reduction temperature, indicating that the core-shell catalyst has a higher strong metal-support interaction.

(5) Under normal pressure, pass CH ₄ , CO ₂ and He into nickel-nickel silicate hollow spheres in a 1:1:1 manner (space velocity 36L·g ^-1 cat·h ^-1 ), respectively And nickel-nickel silicate-SiO ₂ multi-core shell hollow sphere catalyst fixed bed reactor (600 ^o C), the reaction 50h. For the nickel-nickel silicate hollow sphere catalyst, although the initial conversion is slightly higher because of its higher nickel loading. However, the conversion of methane and carbon dioxide dropped by 36% and 31%, respectively. In comparison, the conversions of methane and carbon dioxide drop by 19% and 22%, respectively, for the nickel-nickel silicate-SiO multicore _- shell hollow sphere catalyst. Thermogravimetric differential thermal analysis shows that the nickel-nickel silicate-SiO ₂ core-shell hollow sphere catalyst has a weight loss of 1/8 of that of the nickel-nickel silicate catalyst, indicating that the former has a high ability to resist carbon deposition.

Example 6:

(1) Mix 200 mL of ethanol, 100 mL of water and 10 mL of sodium silicate at room temperature and stir well. Ammonia was added to adjust the pH to 10. After stirring for 12h, it was separated with a centrifuge. Wash with a mixture of ethanol and water. Finally, silica nanoparticles of 1 µm were obtained, which were dried at 150 degrees for 24 hours.

(2) Take 2g silicon dioxide, 0.3g nickel acetylacetonate, add urea, adjust pH to 12. The mixed solution was put into an autoclave, heated to 120 degrees, reacted for 24 hours, and then cooled to room temperature. Centrifuged, washed with methanol, ethanol, and water, and put it into a drying oven at 100 degrees. Nickel silicate hollow spheres were obtained. The specific area was 328 m ² ·g ^-1 , and the nickel loading was 35 wt %.

(3) Disperse the nickel silicate hollow spheres in a mixed solution of ethanol (30 mL), water (10 mL), and C _n TAB (n=10) (30 mg). After stirring for 30 min, ammonia water (30 mL) was added. After stirring for 30 min, 1 mL of ethyl orthosilicate was added. After reacting at room temperature for 1 h, it was centrifuged and washed three times with a mixed solution of methanol and water. Put it in a drying oven at 100 ^o C to dry for 24h. The nickel silicate-SiO ₂ core-shell hollow spheres were obtained, the thickness of the SiO ₂ shell layer was 20 nm, and the specific surface area was 300 m ² ·g ^-1 .

(4) The nickel silicate-SiO ₂ core-shell hollow spheres were placed in a muffle furnace and calcined at 700 degrees for 4 h. Then pass 15% hydrogen, and reduce at 700 degrees for 0.5h. Finally, a nickel-nickel silicate-SiO ₂ multi-core shell hollow sphere catalyst was obtained. Despite high temperature calcination and reduction, the needle-like nickel silicate phase still exists. It can be seen that in the catalyst obtained by this synthesis method, the nickel silicate is not completely decomposed. The particle size of the highly dispersed nickel is about 7 nm. In addition, compared with the nickel silicate hollow sphere catalyst, the nickel silicate-SiO core _- shell hollow sphere catalyst has a higher reduction temperature, indicating that the core-shell catalyst has a higher strong metal-support interaction.

(5) Under normal pressure, pass CH ₄ , CO ₂ and He into nickel-nickel silicate hollow spheres in a 1:1:1 manner (space velocity 36L·g ^-1 cat·h ^-1 ), respectively And nickel-nickel silicate-SiO ₂ multi-core shell hollow sphere catalyst fixed bed reactor (600 ^o C), the reaction 50h. For the nickel-nickel silicate hollow sphere catalyst, although the initial conversion is slightly higher because of its higher nickel loading. However, the conversion of methane and carbon dioxide dropped by 36% and 31%, respectively. In contrast, for the nickel-nickel silicate-SiO multicore _- shell hollow sphere catalyst, the conversions of methane and carbon dioxide dropped by 30% and 29%, respectively. Thermogravimetric differential thermal analysis shows that the nickel-nickel silicate-SiO ₂ core-shell hollow sphere catalyst has a weight loss of 90% of that of the nickel-nickel silicate catalyst, indicating that the former has high resistance to carbon deposition.

Claims (6)

1. Methane reforming multi-core-shell hollow catalyst nickel-nickel silicate-SiO₂Is characterized in that the nickel-nickel silicate-SiO prepared by the method₂The multi-core-shell hollow catalyst is suitable for the temperature of 600 DEG C^oCH at C₄Dry reforming reaction, the method comprising the steps of:

(1) the ethanol, the water and the silicon source are 0^oC～70^oC, uniformly mixing and stirring, adding alkali liquor to adjust the pH value to 10, stirring, separating by a centrifugal machine, washing, and finally drying to obtain silicon dioxide nano particles;

(2) preparing silicon dioxide nano particles with the particle size of 500 nm-1 mu m into 1 g/L-10 g/L of concentration, adding alkali liquor to adjust the pH to 8-13, adding a nickel precursor with the concentration of 1 g/L-10 g/L, and performing heat treatment at the temperature of 50 DEG C^oC～220^oC, synthesizing under the condition of C, and finally cooling, centrifugally separating and washing to obtain the nickel silicate hollow spheres;

(3) dispersing hollow nickel silicate spheres in a mixed solution of a surfactant and water, adding an alkali solution after stirring, adjusting the pH to 10-14, adding 10mL of ethyl orthosilicate for reaction at room temperature, and finally performing centrifugal separation, washing and drying to obtain nickel silicate-SiO₂A core-shell hollow sphere;

(4) nickel silicate-SiO₂The temperature of the core-shell hollow sphere is 300^oC～800^oReducing the mixture in a hydrogen atmosphere to obtain highly dispersed nickel-nickel silicate-SiO₂A multi-core-shell hollow catalyst;

in the step (2), the nickel precursor is one or a combination of nickel nitrate, nickel acetate, nickel acetylacetonate, nickel oxalate and nickel oleate.

2. The methane reforming multi-core-shell hollow catalyst nickel-nickel silicate-SiO of claim 1₂The preparation method is characterized by comprising the following steps: in the step (1), the silicon source is one or a combination of more of tetraethoxysilane, sodium silicate sodium glass and methyl orthosilicate.

3. The methane reforming multi-core-shell hollow catalyst nickel-nickel silicate-SiO of claim 1₂The preparation method is characterized by comprising the following steps: in the steps (1), (2) and (3), the alkali liquor is one or a combination of several of sodium hydroxide, urea and ammonia water.

4. The methane reforming multi-core-shell hollow catalyst nickel-nickel silicate-SiO of claim 1₂The preparation method is characterized by comprising the following steps: in the steps (1), (2) and (3), the washing solvent used for washing is one or a combination of several of water, ethanol, methanol, acetone and cyclohexane.

5. The methane reforming multi-core-shell hollow catalyst nickel-nickel silicate-SiO of claim 1₂The preparation method is characterized by comprising the following steps: in the step (3), the surfactant is a nonionic surfactant or an ionic surfactant, wherein the nonionic surfactant is C₁₄H₂₂O(C₂H₄O)_n，n=10～15，C₁₅H₂₄O(C₂H₄O)_nN = 5-10; the ionic surfactant is an alkyl quaternary ammonium salt surfactant C_nAnd (3) TAB, wherein n = 10-15.

6. The methane reforming multi-core-shell hollow catalyst nickel-nickel silicate-SiO of claim 1₂The preparation method is characterized by comprising the following steps: in the step (4), the specific surface area of the nickel-nickel silicate-silicon dioxide core-shell hollow catalyst is 300m²•g^-1～600m²•g^-1The thickness of the silicon dioxide shell layer is 30 nm-80 nm.

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